Rotating electrical machines such as, for example, generators, motors, and motor/generators, may include one or more rotors and one or more stators. The rotors may include at least a shaft and a rotor core. The rotor core is typically mounted on the shaft and may include a plurality of salient rotor poles. The number of rotor poles may vary, but the number is generally based on the speed at which the shaft will be rotating and, in the case of a generator, on the frequency of the electric current that is to be generated.
The rotor poles each have copper wire wound thereon, which is typically referred to as the rotor winding. Preferably, the rotor winding is configured to form a complete circuit from the point it enters the first rotor pole to the point it exits the last rotor pole. In many applications, the rotor winding is made of substantially flat, relatively stiff, coiled copper strips. Thus, the ends of the rotor winding between adjacent rotor poles are, in many instances, electrically connected using jumpers. These jumpers are sometimes referred to as rotor pole crossovers.
During machine operation, most notably for machines that rotate at relatively high speeds, substantial centrifugal forces may be exerted on the rotor winding and the rotor pole crossovers. Moreover, during machine startup and shutdown operations, the rotor pole crossovers may undergo potentially stressful mechanical and thermal cycles. The current direction in various applications, including aerospace quality electric power system applications, is toward higher power, higher speed, and lighter weight electrical machines. Thus, the rotor pole crossovers may experience relatively higher centrifugal forces.
The rotor crossovers that are presently used, while generally safe and reliable, do suffer certain drawbacks. For example, present rotor pole crossovers, which are also made from flat wire conductors, typically exhibit a lack of flexibility. As a result, these rotor pole crossovers may crack under the centrifugal forces and the mechanical and thermal cycles encountered during machine operation, startup, and shutdown. Indeed, in some instances, rotor poles crossovers have cracked all the way through, resulting in a loss of rotor electrical field.
Hence, there is a need for a rotor pole crossover for rotating electrical machines that is relatively flexible and/or will not crack under the centrifugal forces that may be exerted thereon during machine operation and/or will not crack under the mechanical and thermal cycles encountered during machine startup and shutdown operations. The present invention addresses one or more of these needs.